Abstract Body: Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by impaired normal cardiovascular adaptation to pregnancy, leading to increased vascular resistance and reduced cardiac output. Previous studies have shown that the pregnant Dahl salt-sensitive (DSS) rat, a model of superimposed preeclampsia, exhibits fetal growth restriction (FGR) during pregnancy. However, the underlying mechanisms are not well understood. In the current study, we investigated whether cardiac adaptations to pregnancy are impaired in DSS rats. Virgin Sprague Dawley (SD; control) and DSS rats were implanted with telemetry transmitters at 11 weeks of age (WOA) and baseline BP measured (n=5/group). At 12 WOA, virgins mated overnight with male rats of the same strain. The presence of a sperm plug the next day was indicative of pregnancy and considered gestation day (GD) 0. Blood pressure was measured throughout gestation. Cardiac function was assessed in timed-pregnant SD and DSS rats via echocardiogram at baseline (as virgins), GD10, and GD18. On GD19, dams were sacrificed, blood, tissues, and fetal and placental measurements were collected. At baseline, MAP was similar between SD and DSS rats. By GD18, MAP was significantly higher in DSS rats (142±4mmHg) compared to SD rats (102±2mmHg; p<0.001). During pregnancy, MAP increased by 12±4mmHg in DSS rats, whereas SD rats displayed a significant decrease of 23±6mmHg. On GD10 and GD18, cardiac output was increased by +31.1±4.5% and +38.0±7.8%, respectively in SD rats compared to baseline. However, in DSS rats cardiac output on GD10 (+0.5±12.6%) and GD18 (-1.2±6.3%) did not show the normal pregnancy induced adaptations. Stroke volume significantly increased in pregnant SD from 175.2±4.1 µL at baseline to 236.2±13.1µL on GD18 (p<0.01), but was not changed in DSS rats (baseline: 208±3.4µL vs GD18: 198.1±8.1 µL; n.s). Impairments in systolic adaptation were associated with poor fetal outcomes in DSS rats. Placental efficiency (SD: 5.7±0.6g vs DSS: 3.8±0.2g; p<0.05), fetal weight (SD: 3.1±0.4g vs DSS: 2.0±0.1g; p<0.05), crown to rump length (SD: 3.4±0.2cm vs DSS: 2.7±0.1cm; p<0.05), and abdominal circumference (SD: 3.0±0.2cm vs DSS: 2.3±0.1g; p<0.01) were all significantly reduced in DSS rats compared to SD rats. These findings highlight impaired systolic function in the DSS rat during pregnancy and suggest an association between deficient maternal cardiac adaptation with placental insufficiency and FGR in superimposed PE.